The meniscus, fibrocartilaginous tissue found within the knee joint, is responsible for shock absorption, load transmission, and stability within the knee joint. According to the National Center for Health Statistics, over 600,000 surgeries each year are the result of complications with the meniscus. The meniscus has the intrinsic ability to heal itself; unfortunately, this property is limited only to the vascular portions of the tissue. For damage outside of these areas and overall degeneration of the tissue, methods need to be developed that will assist the meniscus in healing itself Sweigart M A Tissue Eng 7(2), 111-29 (April 2001).
Degeneration of articular cartilage in osteoarthritis is a serious medical problem caused by arthritis, both rheumatoid and osteoarthritis. Drugs are given to control the pain and to keep the swelling down, but the cartilage continues to be destroyed. Eventually, the joint must be replaced. It is still unknown why cartilage does not heal and no solutions to this problem are known Mankin, N. E. J. Med. 331(14), 940-941 (October 1994). Soon after superficial injury, chondrocytes adjacent to the injured surfaces show a brief burst of mitotic activity associated with an increase in glycosaminoglycan and collagen synthesis. Despite these attempts at repair, there is no appreciable increase in the bulk of cartilage matrix and the self repair process is usually ineffective in healing the defects.
Osteochondral, or full-thickness, cartilage defects expand into the subchondral bone. Such defects arise after the detachment of osteochondritic dissecting flaps, fractured osteochondral fragments, or from chronic wear of degenerative articular cartilage. Osteochondral defects depend on the extrinsic mechanism for repair. Extrinsic healing relies on mesenchymal elements from subchondral bone to participate in the formation of new connective tissue. This fibrous tissue may or may not undergo metaplastic changes to form fibrocartilage. Even if fibrocartilage is formed, it does not display the same biochemical composition or mechanical properties of normal articular cartilage or subchondral bone and degenerates with use, Furukawa, et al., J. Bone Joint Surg. 62A, 79 (1980); Coletti, et al., J. Bone Joint Surg. 54A, 147 (1972); Buckwalter, et al., “Articular cartilage: composition, structure, response to injury and methods of facilitating repair”, in Articular Cartilage and Knee Joint Function: Basic Science and Arthroscopy, Ewing J E, Ed., (New York, Raven Press, 1990), 19.
Injection of dissociated chondrocytes directly into the site of the defect has also been described as a means for forming new cartilage, as reported by Brittberg, et al., N. E. J. Med. 331, 889-895 (October 1994). Cartilage was harvested from minor load-bearing regions on the upper medial femoral condyle of the damaged knee, cultured, and implanted two to three weeks after harvesting.
Moreover, if the defect includes a part of the underlying bone, this is not corrected by the use of chondrocytes. The bone is required to support the new cartilage.
Cartilage grafts are also needed in plastic surgery like in rhinoplasty, and the reconstruction of ears.
The possibility of using stem cells was also examined. Stem cells are cells which are not terminally differentiated, which can divide without limit, and divide to yield cells that are either stem cells or which irreversibly differentiate to yield a new type of cell. Unfortunately, there is no known specific inducer of the mesenchymal stem cells that yields only cartilage. In vitro studies in which differentiation is achieved using different bioactive factors or molecules, yields differentiation of the cells to cartilage which eventually calcified and turned into bone.
Thus, there is a need to have a method and composition for the formation or repair of a cartilage or a bone. In another embodiment, it will be highly advantageous to have a cell which can divide and form a cartilage or a bone tissue.